The present invention relates to absorbent articles such as sanitary napkins, adult incontinence devices, and the like. The absorbent articles have a central absorbent element that is adapted to be worn in a crotch portion of a wearer""s undergarment and are provided with a pair of flaps, one flap extending laterally from each respective longitudinal side of the central absorbent element. The flaps are flexible and adapted to be folded over the edges of a wearer""s undergarment. A central portion of the flap is formed from a substantially non-extensible flexible material and adjacent corner portions of the flap are formed from flexible, elastic materials having an elastic modulus.
Numerous types of absorbent articles for the absorption of body fluids such as menses, urine, and feces are well known in the art. Absorbent articles, particularly sanitary napkins, having flexible side flaps (which are also commonly referred to as wings or tabs) are disclosed in the literature and are commercially available.
In general, the flaps extend laterally from a central absorbent element and are adapted to be folded around the edges of the wearer""s undergarment in the crotch region when in use. Thus, in use the flaps are disposed between the edges of the wearer""s undergarment in the crotch region and the wearer""s thighs. Commonly, the flaps are provided with an attachment means for affixing the flaps to the underside of the wearer""s undergarment. The flaps serve to prevent exudates from soiling the edges of the wearer""s undergarment and to help stabilize the napkin from shifting out of place.
Sanitary napkins having flaps of the various types are well known in the art. While sanitary napkins having flaps are commonly viewed as providing better protection against soiling as compared to sanitary napkins without flaps, the napkins having flaps commonly experience problems that keep them from being optimally effective. These problems generally result from the stresses exerted on the flaps from a wearer""s undergarment when the sanitary napkins are worn.
More particularly, when the flaps are folded over the edges of the wearer""s undergarment, stresses are imparted by the user""s undergarment to the corner regions of the flaps. That is, the stresses are especially high along the fold line at the edges of the wearer""s undergarment where the flaps are folded from the body-side of the undergarment to the underside of the undergarment due to an inability of a linearly folded flap to accommodate the curved configuration of the crotch portion of the undergarment. These stresses are magnified when a wearer sits or crouches because the edges of the undergarment are pulled outward against the flaps thus increasing the forces against this fold line. When the stresses become too high, the flaps may become detached from the undergarment and some portion of the aforementioned benefits of the flaps may be lost. In addition, even if the stresses are not sufficient to detach the flaps, they may still be sufficient to cause the flaps to bunch longitudinally creating creases in a proximal portion of the flap. This effectively reduces the length of the flaps and thus reduces the area of coverage of the wearer""s undergarments. The stresses described above can also unduly limit the size of the flaps used with an absorbent article since the stresses are typically greater in products having large flaps (that is flaps having a relatively large longitudinal dimension). Thus, there is a need for a way of eliminating or substantially reducing the stresses that develop in the flaps in use, so as to prevent them from becoming detached from the wearer""s undergarment and losing ability to cover a given area of the undergarment.
A number of variations on the types of flaps described above have been presented in an attempt to solve various problems. For example, sanitary napkins have been provided with flaps affixed inward from the longitudinal edge of the napkin, sanitary napkins have been provided with elastic means for providing greater convex shape to the body-facing portion of the central absorbent and for enabling adhesive-free placement of the flaps of the napkin. Sanitary napkins have been provided with longitudinally expandable flaps and sanitary napkins have been provided with laterally extensible zones in the flaps. While these approaches serve to help relieve the stresses that occur when flaps fold along a curved undergarment crotch, the invention requires the formation of excess material along the second portion of the flap. Since this material is devoid of elastic memory, the excess is present whether it is required by the particular shape of the undergarment or not, thus presenting the possibility of discomfort to the wearer owing to bunching of the excess material. Thus there is a need to correct the weaknesses of the prior known designs such as described above.
It is an object of this invention to provide an absorbent article having side flaps that are adapted to be folded over a crotch portion of an undergarment, the flaps being adapted to relieve stresses that may develop in the corner regions of the flap.
In accordance with the present invention, there has been provided a sanitary napkin comprising a central absorbent element having a cover layer, a barrier layer and an absorbent core between the cover layer and the barrier layer, the central absorbent element having opposite longitudinally extending edges and opposite lateral ends,
a flap extending laterally from each respective longitudinal edge along a line of juncture and adapted to be folded over a crotch portion of an undergarment in use, each flap having a central region and a corner region adjacent the line of juncture and a lateral centerline extending through the central region and bisecting the flap into first half and a second half;
the central region of the flap adjacent the flap lateral centerline being formed from a layer of a non-tensioned flexible, elastic film material having an elastic modulus and at least a portion of each corner region being formed from a substantially non-elastic material wherein the central region is capable of elastically expanding in use to permit each corner region to smoothly conform to the crotch portion of the undergarment.